The politics of replacing Supreme Court Justice Antonin Scalia is becoming a major issue in the re-election campaign of U.S. Sen. Mark Kirk, R-Ill., who is locked in a tough Nov. 8 showdown against Democratic challenger U.S. Rep. Tammy Duckworth, D-Illinois.

Kirk, widely considered one of the most vulnerable GOP senators up for re-election, made waves last week when he broke with his party’s leadership to call for a vote on President Obama’s Supreme Court selection, appellate Judge Merrick Garland.

“It’s just man up and cast a vote,” Kirk said.

Scalia died Feb. 13 while staying at a private hunting ranch in Texas.

Kirk, a moderate who in 2010 won the seat once occupied by Obama, announced Monday that he plans to meet with Garland at 2 p.m. Tuesday at the Senate Office Building.

Kirk will be the first GOP senator to meet with Garland. So far a dozen Republican senators, including Kirk, have said they’d be willing to sit down with the appellate court judge.

“Illinois voters demand that their elected officials offer independent and thoughtful leadership that puts the people of Illinois first all the time,” according to a statement from his campaign. Kirk said he “looks forward to meeting with Judge Merrick Garland and remains hopeful that there will be a fair and thorough hearing along with a complete and transparent release of all requested information.”

But Kirk has not said whether he intends to lobby Mitch McConnell, the Senate majority leader, to hold hearings and a vote on Garland. McConnell so far has not budged from his initial declaration that the Senate Judiciary Committee won’t consider a Supreme Court nominee until after the next president take office in January.

Duckworth, who represents a House district in suburban Chicago, said she has been the one pressing for a vote on Garland.

Kirk “still hasn’t actually pressured Mitch McConnell. He still hasn’t gone on record to pressure the leadership to hold this vote. And frankly, it’s their constitutional duty to review and advise and have this vote,” Duckworth said of the Senate.

Illinois voters demand that their elected officials offer independent and thoughtful leadership that puts the people of Illinois first all the time.

U.S. Sen. Mark Kirk, R-Illinois

The Kirk campaign issued a statement Friday that accused Duckworth of engaging “in a series of false and misleading statements to hide the fact that she is ranked as one of the most partisan and least-effective members of Congress. The simple fact is that Senator Kirk is considered one of the most thoughtful and independent members of Congress and that is demonstrated in his public support for a hearing and a vote on Judge Garland’s nomination.”

Kirk’s re-election fight occurs at a time when Senate Republicans are seeking to hold on to their 54-46 seat advantage, including two independents who caucus with the Democrats. Republicans are trying to defend 24 of those seats, versus 10 seats held by Democrats.

Meanwhile, most Americans think the Senate should hold a vote on Garland, according to the most recent polling. new details from a CBS News/New York Times. Just over half, or 53 percent, of Americans surveyed would like the Senate to vote on the Garland pick, while 42 percent believe they should wait until the next president is chosen, according to a CBS News poll out last week.

Perhaps even more worrisome for Republicans, 69 percent of the public feel the Senate should hold hearings on the nomination. Just 25 percent say that the Senate should not consider the nomination, according to a poll released March 21 by Monmouth University in New Jersey.

Majorities of Democrats (85 percent), independents (66 percent), and Republicans (56 percent) alike say that Garland should get a hearing, according to the Monmouth poll.

Likely to be hurt in the stand-off between Obama and the Senate are moderate Republican candidates in heavily Democratic states such as Kirk, who in a profile late last year on the website Politico was described as a “a centrist on social issues and a hawk on foreign policy.”

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The Politico article also described Kirk as a member of the “shrinking number of moderate Republicans in Congress” and underscored how he, in his campaign against Duckworth, “is in the fight of his political career — the most vulnerable Republican senator on the ballot next year who occupies one of five seats Democrats must win to take back the Senate.”

It hasn’t helped Kirk that he suffered a serious stroke in 2012 that kept him off the Senate floor for almost a year. Also hurting Kirk is the fact that in a year that Illinois native Hillary Clinton will be the likely Democratic presidential nominee, he is running against a female Democrat who served as an Army helicopter pilot and who lost both legs after her helicopter got shot down in Iraq in 2004. Kirk’s stroke has forced him to regularly use a wheelchair, and has also slurred his speech.

Kent Redfield, professor emeritus of political science at the University of Illinois-Springfield, said Kirk’s announcement that he planned to meet with Garland was “good politics in terms of both distancing himself from kind of whatever the Republicans are doing. ... And it is in keeping with the public image, the political image that he has constructed.”

But Kirk’s efforts to portray himself as a moderate might not be enough to salvage his re-election hopes when it comes to raising money from big Republican donors. Because he is considered one of the most “endangered” Republicans seeking re-election, Kirk might lose out if Republican donors perform “triage” in a tough political year, especially if Donald Trump — a candidate with historically high unfavorable ratings among women and minority voters —is the presidential nominee who sits atop the GOP ticket, according to Redfield.

(Kirk) still hasn’t actually pressured Mitch McConnell. He still hasn’t gone on record to pressure the leadership to hold this vote. And frankly, it’s their constitutional duty to review and advise and have this vote.

U.S. Rep. Tammy Duckworth, D-Illinois

“If they’re going to do triage in a bad Republican year, then he is one of the ones that might get the short end of that,” Redfield said. “He is certainly going to have a much more difficult time holding onto his seat than some of the other Republican targets. ... This is going to be a very, very tough race for Kirk.”

Madison Case, a non-partisan political communications consultant, Kirk really had no choice but to come out in favor of at least holding a hearing on the Garland nomination.

Part of the reason for Kirk’s move to push for a Garland hearing stems from the fact the U.S. Senate is getting lambasted by criticism that it is not doing its job. Marco Rubio, the GOP senator from Florida, took deep hits to his popularity because of his failure to show up for many votes in the Senate, Case said.

“They hit (Rubio) really hard for not doing his job as a senator,” Case said. “There is such a displeasure from the American people about senators not doing their job. And in my opinion that’s part of the reason for such a poor approval rating of senators right now. So Kirk has no choice but to come forward and say in a very Democratic state they should at least hear this pick, which they say is a consensus nominee.”

No matter what Kirk says or does, however, as long the Senate refuses to hold a hearing on the Garland pick, it will only hurt vulnerable GOP candidates such as Kirk, she said.

“The Republican Party is only reinforcing they are the party of no,” Case said. “The Republicans created this problem for themselves. They cemented themselves as the party of no. And they will continue that narrative through Obama’s term, and it can only be to their detriment.”